Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$46.83	11.314%	$52.1283	$52.13	$52.15	$52.10
Purchase #2	$158.43	4.789%	$166.0172	$166.02	$166.00	$166.00
Purchase #3	$244.69	9.300%	$267.4462	$267.45	$267.45	$267.40
Purchase #4	$148.26	4.833%	$155.4254	$155.43	$155.45	$155.40
Purchase #5	$162.42	6.682%	$173.2729	$173.27	$173.25	$173.30
Purchase #6	$174.45	12.515%	$196.2824	$196.28	$196.30	$196.30
Purchase #7	$139.92	6.753%	$149.3688	$149.37	$149.35	$149.40
7 purchase totals =	$1,075.00		$1,159.9412	$1,159.95	$1,159.95	$1,159.90